The present invention relates to construction equipment, and more particularly to a control system that monitors the health of a pressure sensor associated with the construction equipment.
Construction equipment often has several different systems that depend on the powerplant (typically an internal combustion engine) for power. Often these systems will include a hydraulic system to control various implements and a powertrain system to propel the machine. For example, on wheel loaders the powerplant must provide power to the powertrain to propel the machine and must provide power to the hydraulic system to control the bucket. Often these two systems require power simultaneously. For example when a wheel loader loads the bucket with material, the powertrain requires power to propel the machine into the pile of material, and the implement system requires power to lift the rock or soil. It is desirable to select a powerplant that can provide enough power to permit both systems to function efficiently when operating together. However, a powerplant with enough power to operate both systems at the same time could be capable of producing more power than necessary if only one of the systems was demanding power. In the past, some wheel loaders have simply used powertrains and implement systems that are able to withstand the full power output of the powerplant. However, this results in more expensive, heavier and generally less responsive powertrain.
In other prior art systems, there have been attempts to modify the power output of the engine based on powertrain and implement demands. In such systems, the power output of the engine is limited when there is no power required by the implement system. This in turn prevents the powerplant from producing more power than the powertrain is capable of receiving, without having to use the more expensive, heavier, less responsive powertrain. Although these systems have generally worked well there are drawbacks in the way they have attempted to determine the power demanded by the implement system, or the powertrain. Some systems have used pressure sensors to measure the hydraulic pressure provided to the implements and have determined the power demanded by the implement from that measurement. However, these systems are sometimes unable to detect when the sensors fail, especially if the sensor continues to produce what appears to be a valid signal. If the sensors fail and continue to produce an erroneous signal that otherwise appears valid, the control system will nevertheless use the signal to determine the maximum engine power output. These systems could then either produce too much power for the powertrain or inappropriately limit power output of the engine.
It would be preferable to have a fault tolerant control system, that could reliably determine whether the implement was demanding power from the powerplant.
An embodiment of the present invention includes a control system capable of generating a diagnostic fault in response to a failed hydraulic pressure sensor. Preferably the system determines the hydraulic pressure in a low load condition and then determines the hydraulic pressure in a high load condition. The system then evaluates the pressure sensor performance in response to the determined hydraulic pressures.
These and other aspects and advantages associated with the present invention will become apparent to those skilled in the art upon reading the following detailed description in connection with the drawings and appended claims.